The quantitative determination of analytes in body fluids is of great importance in the diagnoses and maintenance of certain physiological abnormalities. For example, lactate, cholesterol and bilirubin should be monitored in certain individuals. In particular, it is important that diabetic individuals frequently check the glucose level in their body fluids to regulate the glucose intake in their diets. The results of such tests can be used to determine what, if any, insulin or other medication needs to be administered. In one type of blood-glucose testing system, test sensors are used to test a sample of blood.
A test sensor contains biosensing or reagent material that reacts with blood glucose. One type of electrochemical test sensor is a multilayer test sensor that includes a base or substrate and a lid. Another type of electrochemical test sensor includes a base, a spacer and a lid. Existing electrochemical test sensors include at least two electrodes in the form of an electrode pattern. A potential is applied across these electrodes and a current is measured at the working electrode. The current measurement is directly proportional to the size of the working electrode.
The accuracy of the electrochemical test sensor is typically improved if the area of the working electrode can be precisely defined in the test-sensor manufacturing process. Currently, an electrode pattern (including the working electrode) is typically defined on a base on one axis by the electrode-defining technique (i.e., printing or laser-ablation) and the other axis is defined by a second layer (a lid or a spacer) that is attached to the base. The act of attaching the base and the lid or spacer often has high, less desirable tolerances. For example, the laminating of the base and the lid or spacer tends to have variances that are less than desirable (i.e., +/−0.005 in.). The use of laser-ablation, on the hand, has a more desirable tolerance (i.e., +/−0.0005 inch). Thus, the tolerance in the lid or spacer placement then becomes the significant factor influencing the precision of forming the working-electrode area.
Therefore, it would be desirable to use a method that improves the accuracy of the test-sensor-based system by better defining the working electrode. It would also be desirable to enhance the within-lot reproducibility of the manufacturing process.